Purification and characterization of biosurfactants from Nocardia sp. L-417

The Nocardia sp. L-417 strain grown with n-hexadecane as a carbon source produced two types of biosurfactant that have different characteristics. These biosurfactants were purified by procedures that included ammonium sulphate fractionation, chilled acetone and hexane treatments, silica-gel column chromatography and Sephadex LH-20 gel filtration. The purified biosurfactants were very stable over a broad range of pHs (2-12) and temperatures (100 degrees C, 3 h). The biosurfactant type I had strong properties as an emulsifying agent and as an emulsion-stabilizing agent, whereas type II had a strong ability to reduce surface tension.